Hello All, This will be what WHAT I THINK about corner markers, They were placed at the corners of a league square, seems to be boulders aprox 6 / 8 feet high and 6 / 10 feet long, some are smaller some may be larger, they can be flat, on edge as the one that was recently posted, ( a side view would be nice ) they can be just boulders but they will have some kind of mark to identify them anything will do, and should have something to indicate at least 3 directions of travel, hopeful 4, if not then it indicates the line between the 25 square block distance between trail markers on those may be 480 feet, Large corner markers can possibly be seen from a greater perhaps 2.5 miles, trail markers between the corners markers be 40 inches or so and be large enough to be seen from that distance, no tricks, just plain ole trail markers such as a pig walking, anything you find sitting down or a head is not a trail marker its just saying look this way. The directions should be N. S. E. W. compass degrees is another clue, your corners will be sitting or resting, something on a nest, Its easy it only took me 45 years. Yes they very possibly all had cache sites,